For a moment, near the end, the only sound was a lone person breathing. It was the sound of someone committing an unfathomable act. And then the screams of 149 people filled the air.

There will be time to discuss exactly what happened on Germanwings Flight 9525, which on Tuesday crashed into the French Alps, apparently at the direction of its co-pilot. There will be time to debate how to respond -- how cockpit doors should be locked, how pilots should be screened, how much authority a flight crew should have. And there will be time to plumb the psyche of Andreas Lubitz, the 28-year-old co-pilot who investigators say locked his commander out of the cockpit and directed the plane to its terrible descent.

For now, it's enough simply to observe that he was a human being -- and as such was subject to the bewildering matrix of emotions, motives and anxieties that roil the human soul. That's part of what makes this crash so awful: It crystallizes the one danger that no amount of metal detectors, security guards or preflight lectures could ever prevent.

Humans often behave irrationally. We panic, succumb to depression, embrace extremism. We're impulsive and prone to error. We fall asleep and lose focus. In short, we make mistakes.

For all these reasons, the act of flying has been increasingly automated over the years, so much so that even working pilots can get rusty. And yet -- even in an age of drone deliveries and pilotless Predators -- one young man with the wrong intent is capable of bringing down a jet in a matter of minutes.

Someday, the skies may be largely free of human pilots, and planes will cruise with robotic efficiency from takeoff to landing. Such a system would have complications and consequences all its own, of course. And it would surely still require input and supervision from people. But it may be the best way to mitigate the risks of the most maddening, illogical and stubbornly unpredictable aspect of aviation: the human element.

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